The present invention relates to a semiconductor processing apparatus and method for the thermal processing of thin film applications on a semiconductor substrate, such as a semiconductor wafer, in which the temperature of the substrate can be accurately controlled to minimize the diffusion of the impurities in the substrate to achieve junctions that produce higher speed devices than heretofore known.
In electronic device fabrication, gases containing impurities, such as arsenic, phosphorous, boron, or the like, are injected onto a semiconductor substrate, such as a polysilicon wafer, to implant impurities in the substrate. In order to activate the impurities so that they become part of the lattice structure of the substrate, and therefore form the junctions that create electronic devices, the semiconductor substrate is typically heated to relatively high temperatures.
The heat that is required to achieve activation of the reactant gas impurities with the lattice structure of the semiconductor substrate, such as a polysilicon wafer, and to form junctions in the substrate, also contributes to diffusion of the impurities through the substrate. With increased diffusion, the electrical performance of the devices is significantly degraded.
One solution is to localize the temperature on the device side of the substrate to control diffusion. However, at these elevated processing temperatures, localized heating generates extremely large vertical temperature gradients though the substrate. These vertical temperature gradients produce thermal moments in the substrate, which cause defects that detrimentally effect current leakage in the devices.
Consequently, there is a need for a processing reactor and method of high temperature processing of a semiconductor substrate that can deliver heat to the substrate in manner to achieve thinner junctions and, therefore, create faster devices, while maintaining the vertical thermal stresses in the substrate at acceptable levels.